async function getAllPeopleImage(backend_domain_name, imageName) {
    // imageName 的值只能为 1.png 2.png 3.png 4.png 5.png 6.png
    const url = backend_domain_name + '/index/get_all_people_image/' + encodeURIComponent(imageName);
    try {
        const response = await fetch(url);
        const blob = await response.blob();
        return URL.createObjectURL(blob);
    } catch (error) {
        console.log(error);
        return null;
    }
}
async function getIcons(backend_domain_name, icon_name){
    // icon_name 只能为 AiKeTangJiaoXuePingCeXiTong.png AiWorkShop_icon.png
    const url = backend_domain_name + '/index/get_icon/' + encodeURIComponent(icon_name);
    try {
        const response = await fetch(url);
        const blob = await response.blob();
        return URL.createObjectURL(blob);
    } catch (error) {
        console.log(error);
        return null;
    }
}
async function getQrCode(backend_domain_name, qr_code_name){
    // qr_code_name 只能为 my_wechat_qr_code.png
    const url = backend_domain_name + '/index/get_qr_code/' + encodeURIComponent(qr_code_name);
    try {
        const response = await fetch(url);
        const blob = await response.blob();
        return URL.createObjectURL(blob);
    } catch (error) {
        console.log(error);
        return null;
    }
}
async function getEdubotTeacherImage(backend_domain_name, teacher_name){
    // The value of the teacher_name can only be wang_lin.png, wang_fei_fan.png or xie_zhi_xin.png
    const url = backend_domain_name + '/index/get_edubot_teacher_image/' + encodeURIComponent(teacher_name);
    try {
        const response = await fetch(url);
        const blob = await response.blob();
        return URL.createObjectURL(blob);
    } catch (error) {
        console.log(error);
        return null;
        }
}